Minimized stanza.lua from Prosody, containing a fix/workaround, for use with prosody_to_xep227.lua https://gist.github.com/bseibold/5041603

mystanza.lua

-- Prosody IM
-- Copyright (C) 2008-2010 Matthew Wild
-- Copyright (C) 2008-2010 Waqas Hussain
-- 
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--


local t_insert      =  table.insert;
local t_concat      =  table.concat;
local t_remove      =  table.remove;
local t_concat      =  table.concat;
local s_format      = string.format;
local s_match       =  string.match;
local tostring      =      tostring;
local setmetatable  =  setmetatable;
local getmetatable  =  getmetatable;
local pairs         =         pairs;
local ipairs        =        ipairs;
local type          =          type;
local next          =          next;
local print         =         print;
local unpack        =        unpack;
local s_gsub        =   string.gsub;
local s_char        =   string.char;
local s_find        =   string.find;
local os            =            os;

local getstyle, getstring;

local xmlns_stanzas = "urn:ietf:params:xml:ns:xmpp-stanzas";

module "mystanza"

stanza_mt = { __type = "stanza" };
stanza_mt.__index = stanza_mt;
local stanza_mt = stanza_mt;

function stanza_mt:add_direct_child(child)
        if type(child) == "table" then
                t_insert(self.tags, child);
        end
        t_insert(self, child);
end

function stanza_mt:add_child(child)
        local last_add = self.last_add;
        (last_add and last_add[#last_add] or self):add_direct_child(child);
        return self;
end


local xml_escape
do
        local escape_table = { ["'"] = "&apos;", ["\""] = "&quot;", ["<"] = "&lt;", [">"] = "&gt;", ["&"] = "&amp;" };
        function xml_escape(str) return (s_gsub(str, "['&<>\"]", escape_table)); end
        _M.xml_escape = xml_escape;
end

local function _dostring(t, buf, self, xml_escape, parentns)
        local nsid = 0;
        local name = t.name
        t_insert(buf, "<"..name);
        for k, v in pairs(t.attr) do
                if s_find(k, "\1", 1, true) then
                        local ns, attrk = s_match(k, "^([^\1]*)\1?(.*)$");
                        nsid = nsid + 1;
                        t_insert(buf, " xmlns:ns"..nsid.."='"..xml_escape(ns).."' ".."ns"..nsid..":"..attrk.."='"..xml_escape(v).."'");
                elseif not(k == "xmlns" and v == parentns) then
                        if type(v) == "table" and #v == 0 then
                                t_insert(buf, " "..k.."=''");
                        else
                                t_insert(buf, " "..k.."='"..xml_escape(v).."'");
                        end
                end
        end
        local len = #t;
        if len == 0 then
                t_insert(buf, "/>");
        else
                t_insert(buf, ">");
                for n=1,len do
                        local child = t[n];
                        if child.name then
                                self(child, buf, self, xml_escape, t.attr.xmlns);
                        else
                                t_insert(buf, xml_escape(child));
                        end
                end
                t_insert(buf, "</"..name..">");
        end
end
function stanza_mt.__tostring(t)
        local buf = {};
        _dostring(t, buf, _dostring, xml_escape, nil);
        return t_concat(buf);
end

function deserialize(stanza)
        -- Set metatable
        if stanza then
                local attr = stanza.attr;
                for i=1,#attr do attr[i] = nil; end
                local attrx = {};
                for att in pairs(attr) do
                        if s_find(att, "|", 1, true) and not s_find(att, "\1", 1, true) then
                                local ns,na = s_match(att, "^([^|]+)|(.+)$");
                                attrx[ns.."\1"..na] = attr[att];
                                attr[att] = nil;
                        end
                end
                for a,v in pairs(attrx) do
                        attr[a] = v;
                end
                setmetatable(stanza, stanza_mt);
                for _, child in ipairs(stanza) do
                        if type(child) == "table" then
                                deserialize(child);
                        end
                end
                if not stanza.tags then
                        -- Rebuild tags
                        local tags = {};
                        for _, child in ipairs(stanza) do
                                if type(child) == "table" then
                                        t_insert(tags, child);
                                end
                        end
                        stanza.tags = tags;
                end
        end

        return stanza;
end

return _M;